Quick electronics question

[cropwell]

I can't see what it is supposed to do! I presume it is some sort of switchable state indicator for the 12-24v and you don't want it to interfere with the logic of the 12-24v line. Do you have any resistor values yet. I presume that you are intending to use a small signal NPN, in which case you will need a current limiting resistor to stop the magic smoke (or is the 12-24v line already limited).

[Kitwn]

m_c,
Another option which avoids the risk of reverse breakdown of the LED would be to connect the LED (with a suitable series resistor) to ground after the switch to 5v. This will not fully confirm that the 24v is pulled down but will indicate that the circuit has been operated.
I assume that 'switch' isn't really a switch (otherwise you'd be switching the 24v directly) so you would have to confirm the actual device can deliver the LED current as well as the base current of the transistor.

If you stick with the design as shown remember that the LED current must be added to the load current when rating the transistor and calculating the base current and hence resistor value.